1. Field of the Invention
The present invention relates to an electrostatic chuck used in a liquid crystal display production apparatus, a CVD production apparatus, or a PVD production apparatus, and particularly relates to a technology to obtain excellent corrosion resistance when the electrostatic chuck is used under high temperature conditions.
2. Related Art
In a semiconductor production process, when a wafer or a substrate is held in a predetermined position to perform accurate temperature control, an electrostatic chuck is generally used. Recently, according to increasing accuracy and density of semiconductor patterns, the temperatures in semiconductor production processes have been further increased. A plasma gas used in the process also tends to be changed from a conventional C2F6 gas to a NF3 gas which has a higher corrosion resistance. As described above, recent semiconductor production processes are performed under severe use environments. Therefore, superior corrosion resistance is required for material used for the electrostatic chuck.
Electrostatic chucks may be categorized into two types: a type in which the major component of a dielectric layer with an absorbent face against the wafer is composed of ceramics and a type in which the major component of the dielectric layer is composed of resin. Moreover, these ceramic types may be further categorized as a sintered electrostatic chuck in which ceramic material is sintered to form the dielectric layer, and as a thermal-sprayed electrostatic chuck in which the ceramic material is thermal-sprayed to form the dielectric layer. These electrostatic chucks are bifurcated, depending on the process used, and various electrostatic chucks have been proposed.
For instance, as a ceramic sintered type, an electrostatic chuck in which major component of a material is aluminum oxide or aluminum nitride and the material is sintered is disclosed (for example, see. Japanese Patent Application Unexamined (KOKAI) Publication No. 11-260534 (p. 3–7, FIG. 1)). As a ceramics thermal-sprayed type, an electrostatic chuck in which a ceramic material of aluminum oxide-titanium oxide is thermal-sprayed to form the dielectric layer is disclosed (for example, see Japanese Patent Publication No. 2971369 (p. 5–7)). A purpose of these disclosed technologies is mainly to improve sorbability of the electrostatic chuck. Specifically, the purpose of the technology described in Japanese Patent Application Unexamined (KOKAI) Publication No. 11-260534 is to improve stabilization of absorbability at high temperatures, and the purpose of the technology described in Japanese Patent Publication No. 2971369 is to improve response of absorbability.
Generally, in a high temperature semiconductor production process in which high level corrosion resistance is required, the ceramic sintered type of electrostatic chuck is used. However, such an electrostatic chuck is expensive because the production process is complex. Furthermore, when such an electrostatic chuck is provided with a heating and cooling system, a process joining the electrostatic chuck and a heating and cooling flange is required. In this case, when the joining is performed by mechanical connection, a temperature control in a semiconductor production process is difficult. When the joining is performed by adhesive bonding, heat resistance and corrosion resistance in a bonded layer cannot be adequately obtained. Furthermore, when the joining is performed by brazing or diffusion bonding, performance of the electrostatic chuck is comparatively high. However, a particular technology is additionally required in the production in this case.
In the ceramic thermal-sprayed type of electrostatic chuck, the joining process can be omitted to directly form the dielectric layer on the heating and cooling flange. Therefore, production cost in this type of the electrostatic chuck can be lower than that in the ceramic sintered type of the electrostatic chuck. However, when a sprayed coating has vacancies at which the sprayed coating is not dense, insulating resistance can be decreased. Therefore, in this case, an impregnant in which the major component is resin must be used to perform a sealing. The insulating resistance is increased due to performing such a sealing. However, when the sealing is performed, destabilization of absorbability by degradation of the impregnant and contamination of the wafer by degradation components occur because the corrosion resistance of the impregnant is low. Moreover, due to such an inadequate corrosion resistance, the ceramic thermal-sprayed type of electrostatic chuck cannot be used in high temperature processes of the semiconductor production process.